One goal of Missouri's Career Ladder program (CL) is to help school districts that have difficulty retaining teachers, particularly those that are small and rural, by offering their teachers opportunities to earn extra pay for extra work and professional development. This report seeks to estimate the effect Career Ladder Program has had on teachers' career decisions, specifically their decisions to stay in a specific school district or to remain in the teaching field. This report presents evidence suggesting that a school district's participation in the Missouri Career Ladder Program would tend to increase retention in the district and the profession, especially for mid-career teachers. The results reported in this paper are especially useful when combined with other findings on this program. Previously reported analyses using 10 years of district-level test score data failed to find evidence for an impact on test scores (Booker and Glazerman 2009). However, focus groups and interviews conducted by Silman and colleagues (Silman and Glazerman) suggest that the program is popular with participating teachers and is run almost entirely by teachers themselves. Thus, when considering the benefits, there was no measurable test score effect, but a positive effect on retention and possibly a positive effect on teacher well-being generated by increasing their incomes by an amount that likely exceeds their hourly rate for the extra work completed. These findings have several implications for the teaching profession. First, they suggest that small bonuses can affect behavior. Second, the magnitudes of the effect estimates remind people that one should not expect "large" effects from small bonuses. Third, the findings suggest that a bonus program that is "not" tied to student performance but offers additional pay for more work for mid-career teachers can make teachers feel better off even if it does not improve their teaching in an easily measurable way. (Contains 7 tables, 2 figures and 3 footnotes.)